Wireless architecture and support for process control systems

ABSTRACT

A wireless communication system for use in a process environment uses mesh and possibly a combination of mesh and point-to-point communications to produce a wireless communication network that can be easily set up, configured, changed and monitored, thereby making a wireless communication network that is less expensive, and more robust and reliable. The wireless communication system allows virtual communication paths to be established and used within the process control system in a manner that is independent of the manner in which the wireless signals are sent between different wireless transmitting and receiving devices within the process plant, to thereby operate in a manner that is independent of the specific messages or virtual communication paths within the process plant. Still further, communication analysis tools are provided to enable a user or operator to view the operation of the wireless communication network to thereby analyze the ongoing operation of the wireless communications within the wireless communication network.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/156,215, filed Jun. 17, 2005 and entitled “Wireless Architecture andSupport for Process Control Systems” which is a continuation-in-part ofpending U.S. application Ser. No. 10/464,087, filed Jun. 18, 2003 andentitled “Self-Configuring Communication Networks for use with ProcessControl Systems” (which is hereby expressly incorporated by referenceherein).

FIELD OF TECHNOLOGY

Methods and apparatuses are disclosed for providing wirelesscommunications within a distributed process control system whichestablish and maintain consistent wireless communication connectionsbetween different remote devices and a base computer in a processcontrol system.

BACKGROUND

Process control systems are widely used in factories and/or plants inwhich products are manufactured or processes are controlled (e.g.,chemical manufacturing, power plant control, etc.). Process controlsystems are also used in the harvesting of natural resources such as,for example, oil and gas drilling and handling processes, etc. In fact,virtually any manufacturing process, resource harvesting process, etc.can be automated through the application of one or more process controlsystems. It is believed the process control systems will eventually beused more extensively in agriculture as well.

The manner in which process control systems are implemented has evolvedover the years. Older generations of process control systems weretypically implemented using dedicated, centralized hardware andhard-wired connections.

However, modern process control systems are typically implemented usinga highly distributed network of workstations, intelligent controllers,smart field devices, and the like, some or all of which may perform aportion of an overall process control strategy or scheme. In particular,most modern process control systems include smart field devices andother process control components that are communicatively coupled toeach other and/or to one or more process controllers via one or moredigital data buses. In addition to smart field devices, modern processcontrol systems may also include analog field devices such as, forexample, 4-20 milliamp (mA) devices, 0-10 volts direct current (VDC)devices, etc., which are typically directly coupled to controllers asopposed to a shared digital data bus or the like.

In a typical industrial or process plant, a distributed control system(DCS) is used to control many of the industrial processes performed atthe plant. The plant may have a centralized control room having acomputer system with user input/output (I/O), a disc I/O, and otherperipherals known in the computing art with one or more processcontrollers and process I/O subsystems communicatively connected to thecentralized control room. Additionally, one or more field devices aretypically connected to the I/O subsystems and to the process controllersto implement control and measurement activities within the plant. Whilethe process I/O subsystem may include a plurality of I/O ports connectedto the various field devices throughout the plant, the field devices mayinclude various types of analytical equipment, silicon pressure sensors,capacitive pressure sensors, resistive temperature detectors,thermocouples, strain gauges, limit switches, on/off switches, flowtransmitters, pressure transmitters, capacitance level switches, weighscales, transducers, valve positioners, valve controllers, actuators,solenoids, indicator lights or any other device typically used inprocess plants.

As used herein, the term “field device” encompasses these devices, aswell as any other device that performs a function in a control system.In any event, field devices may include, for example, input devices(e.g., devices such as sensors that provide status signals that areindicative of process control parameters such as, for example,temperature, pressure, flow rate, etc.), as well as control operators oractuators that perform actions in response to commands received fromcontrollers and/or other field devices.

Traditionally, analog field devices have been connected to thecontroller by two-wire twisted pair current loops, with each deviceconnected to the controller by a single two-wire twisted pair. Analogfield devices are capable of responding to or transmitting an electricalsignal within a specified range. In a typical configuration, it iscommon to have a voltage differential of approximately 20-25 voltsbetween the two wires of the pair and a current of 4-20 mA runningthrough the loop. An analog field device that transmits a signal to thecontrol room modulates the current running through the current loop,with the current being proportional to the sensed process variable.

An analog field device that performs an action under control of thecontrol room is controlled by the magnitude of the current through theloop, which current is modulated by the I/O port of the process I/Osystem, which in turn is controlled by the controller. Traditionaltwo-wire analog devices having active electronics can also receive up to40 milliwatts of power from the loop. Analog field devices requiringmore power are typically connected to the controller using four wires,with two of the wires delivering power to the device. Such devices areknown in the art as four-wire devices and are not power limited, astypically are two-wire devices.

A discrete field device can transmit or respond to a binary signal.Typically, discrete field devices operate with a 24 volt signal (eitherAC or DC), a 110 or 240 volt AC signal, or a 5 volt DC signal. Ofcourse, a discrete device may be designed to operate in accordance withany electrical specification required by a particular controlenvironment. A discrete input field device is simply a switch whicheither makes or breaks the connection to the controller, while adiscrete output field device will take an action based on the presenceor absence of a signal from the controller.

Historically, most traditional field devices have had either a singleinput or a single output that was directly related to the primaryfunction performed by the field device. For example, the only functionimplemented by a traditional analog resistive temperature sensor is totransmit a temperature by modulating the current flowing through thetwo-wire twisted pair, while the only function implemented by atraditional analog valve positioner is to position a valve somewherebetween a fully open and a fully closed position based on the magnitudeof the current flowing through the two-wire twisted pair.

More recently, field devices that are part of hybrid systems becomeavailable that superimpose digital data on the current loop used totransmit analog signals. One such hybrid system is known in the controlart as the Highway Addressable Remote Transducer (HART) protocol. TheHART system uses the magnitude of the current in the current loop tosend an analog control signal or to receive a sensed process variable(as in the traditional system), but also superimposes a digital carriersignal upon the current loop signal. The HART protocol makes use of theBell 202 Frequency Shift Keying (FSK) standard to superimpose thedigital signals at a low level on top of the 4-20 mA analog signals.This enables two-way field communication to take place and makes itpossible for additional information beyond just the normal processvariable to be communicated to/from a smart field instrument. The HARTprotocol communicates at 1200 bps without interrupting the 4-20 mAsignal and allows a host application (master) to get two or more digitalupdates per second from a field device. As the digital FSK signal isphase continuous, there is no interference with the 4-20 mA signal.

The FSK signal is relatively slow and can therefore provide updates of asecondary process variable or other parameter at a rate of approximately2-3 updates per second. Generally, the digital carrier signal is used tosend secondary and diagnostic information and is not used to realize theprimary control function of the field device. Examples of informationprovided over the digital carrier signal include secondary processvariables, diagnostic information (including sensor diagnostics, devicediagnostics, wiring diagnostics, and process diagnostics), operatingtemperatures, a sensor temperature, calibration information, device IDnumbers, materials of construction, configuration or programminginformation, etc. Accordingly, a single hybrid field device may have avariety of input and output variables and may implement a variety offunctions.

More recently, a newer control protocol has been defined by theInstrument Society of America (ISA). The new protocol is generallyreferred to as Fieldbus, and is specifically referred to as SP50, whichis as acronym for Standards and Practice Subcommittee 50. The Fieldbusprotocol defines two subprotocols. An H1 Fieldbus network transmits dataat a rate up to 31.25 kilobits per second and provides power to fielddevices coupled to the network. An H2 Fieldbus network transmits data ata rate up to 2.5 megabits per second, does not provide power to fielddevices connected to the network, and is provided with redundanttransmission media. Fieldbus is a nonproprietary open standard and isnow prevalent in the industry and, as such, many types of Fieldbusdevices have been developed and are in use in process plants. BecauseFieldbus devices are used in addition to other types of field devices,such as HART and 4-20 mA devices, with a separate support and I/Ocommunication structure associated with each of these different types ofdevices.

Newer smart field devices, which are typically all digital in nature,have maintenance modes and enhanced functions that are not accessiblefrom or compatible with older control systems. Even when all componentsof a distributed control system adhere to the same standard (such as theFieldbus standard), one manufacturer's control equipment may not be ableto access the secondary functions or secondary information provided byanother manufacturer's field devices.

Thus, one particularly important aspect of process control system designinvolves the manner in which field devices are communicatively coupledto each other, to controllers and to other systems or devices within aprocess control system or a process plant. In general, the variouscommunication channels, links and paths that enable the field devices tofunction within the process control system are commonly collectivelyreferred to as an input/output (I/O) communication network.

The communication network topology and physical connections or pathsused to implement an I/O communication network can have a substantialimpact on the robustness or integrity of field device communications,particularly when the I/O communications network is subjected toenvironmental factors or conditions associated with the process controlsystem. For example, many industrial control applications subject fielddevices and their associated I/O communication networks to harshphysical environments (e.g., high, low or highly variable ambienttemperatures, vibrations, corrosive gases or liquids, etc.), difficultelectrical environments (e.g., high noise environments, poor powerquality, transient voltages, etc.), etc. In any case, environmentalfactors can compromise the integrity of communications between one ormore field devices, controllers, etc. In some cases, such compromisedcommunications could prevent the process control system from carryingout its control routines in an effective or proper manner, which couldresult in reduced process control system efficiency and/orprofitability, excessive wear or damage to equipment, dangerousconditions that could damage or destroy equipment, building structures,the environment and/or people, etc.

In order to minimize the effect of environmental factors and to assure aconsistent communication path, I/O communication networks used inprocess control systems have historically been hardwired networks, withthe wires being encased in environmentally protected materials such asinsulation, shielding and conduit. Also, the field devices within theseprocess control systems have typically been communicatively coupled tocontrollers, workstations, and other process control system componentsusing a hardwired hierarchical topology in which non-smart field devicesare directly coupled to controllers using analog interfaces such as, forexample, 4-20 mA, 0-10 VDC, etc. hardwired interfaces or I/O boards.Smart field devices, such as Fieldbus devices, are also coupled viahardwired digital data busses, which are coupled to controllers viasmart field device interfaces.

While hardwired I/O communication networks can initially provide arobust I/O communication network, their robustness can be seriouslydegraded over time as a result of environmental stresses (e.g.,corrosive gases or liquids, vibration, humidity, etc.). For example,contact resistances associated with the I/O communication network wiringmay increase substantially due to corrosion, oxidation and the like. Inaddition, wiring insulation and/or shielding may degrade or fail,thereby creating a condition under which environmental electricalinterference or noise can more easily corrupt the signals transmittedvia the I/O communication network wires. In some cases, failedinsulation may result in a short circuit condition that results in acomplete failure of the associated I/O communication wires.

Additionally, hardwired I/O communication networks are typicallyexpensive to install, particularly in cases where the I/O communicationnetwork is associated with a large industrial plant or facility that isdistributed over a relatively large geographic area, for example, an oilrefinery or chemical plant that consumes several acres of land. In manyinstances, the wiring associated with the I/O communication network mustspan long distances and/or go through, under or around many structures(e.g., walls, buildings, equipment, etc.) Such long wiring runstypically involve substantial amounts of labor, material and expense.Further, such long wiring runs are especially susceptible to signaldegradation due to wiring impedances and coupled electricalinterference, both of which can result in unreliable communications.

Moreover, such hardwired I/O communication networks are generallydifficult to reconfigure when modifications or updates are needed.Adding a new field device typically requires the installation of wiresbetween the new field device and a controller. Retrofitting a processplant in this manner may be very difficult and expensive due to the longwiring runs and space constraints that are often found in older processcontrol plants and/or systems. High wire counts within conduits,equipment and/or structures interposing along available wiring paths,etc., may significantly increase the difficulty associated withretrofitting or adding field devices to an existing system. Exchangingan existing field device with a new device having different field wiringrequirements may present the same difficulties in the case where moreand/or different wires have to be installed to accommodate the newdevice. Such modifications may often result in significant plantdowntime.

It has been suggested to use wireless I/O communication networks toalleviate some of the difficulties associated with hardwired I/Onetworks. For example, Tapperson et al., U.S. patent application Ser.No. 09/805,124 discloses a system which provides wireless communicationsbetween controllers and field devices to augment or supplement the useof hardwired communications. However, most, if not all, wireless I/Ocommunication networks actually implemented within process plants todayare implemented using relatively expensive hardware devices (e.g.,wireless enabled routers, hubs, switches, etc.), most of which consume arelatively large amount of power. Further, intermittent interferences,such as the passing of trucks, trains, environmental or whether relatedconditions, etc., make wireless communication networks unreliable andtherefore problematic.

In addition, known wireless I/O communication networks, including thehardware and software associated therewith, generally use point-to-pointcommunication paths that are carefully selected during installation andfixed during subsequent operation of the system. Establishing fixedcommunication paths within these wireless I/O communication networkstypically involves the use of one or more experts to perform anexpensive site survey that enables the experts to determine the typesand/or locations of the transceivers and other communication equipment.Further, once the fixed point-to-point communication paths have beenselected via the site survey results, one or more of the experts mustthen configure equipment, tune antennas, etc. While the point-to-pointpaths are generally selected to insure adequate wireless communications,changes within the plant, such as the removal or addition of equipment,walls, or other structures may make the initially selected paths lessreliable, leading to unreliable wireless communications.

While wireless I/O communication networks can, for example, alleviatethe long term robustness issues associated with hardwired communicationpaths, these wireless I/O communication networks are relativelyinflexible and are considered by most in the process control industry tobe too unreliable to perform important or necessary process controlfunctions. For example, there is currently no easy manner of tellingwhen a wireless communication is no longer functioning properly, or hasdegraded to the point that communications over the wireless link arelikely to be unreliable or to cease altogether. As a result, currentprocess control operators have very little faith in wirelesscommunication networks when implemented for important and necessaryprocess control functions.

Thus, due to the costs associated with installing a wireless I/Ocommunication network (e.g., site surveys, expert configuration, etc.),and the relative little amount of faith that current process controlsystem operators have in wireless communications, wireless I/Ocommunication networks are often cost prohibitive for what they provide,particularly for relatively large process control systems such as thosetypically used in industrial applications.

SUMMARY OF THE DISCLOSURE

A wireless communication architecture for use in a process controlsystem is disclosed which includes the use of mesh and possibly acombination of mesh and point-to-point communications to produce a morerobust wireless communication network that can be easily set up,configured, changed and monitored, to thereby make the wirelesscommunication network more robust, less expensive and more reliable. Thewireless communication architecture is implemented in a manner that isindependent of the specific messages or virtual communication pathswithin the process plant and, in fact, the wireless communicationnetwork is implemented to allow virtual communication paths to beestablished and used within the process control system in a manner thatis independent of the manner in which the wireless signals are sentbetween different wireless transmitting and receiving devices within theprocess plant.

In a refinement, one or more environmental nodes are used to control andoptimize the operation of the wireless communication network. Theenvironmental node(s) are linked to field “environmental” devicesproviding signals indicative of one or more environmental factors suchas temperature, barometric pressure, humidity, rainfall and radiofrequency (RF) ambient noise, amongst other environmental factors thatcould alter the operation of the network.

In another refinement, the network includes a main controller linked toa wireless card. The wireless card is in communication with a repeaternode which, in turn, is in communication with a field node. The fieldnode is linked to a plurality of field devices. In another refinement,the repeater node is eliminated. In another refinement, an environmentalnode and environmental detection devices as discussed above areincorporated with or without one or more repeater nodes. In a furtherrefinement, the field and environmental nodes include a plurality ofports for communication with the field devices.

In a refinement, the wireless communication network is set up totransmit HART communication signals between different devices within theprocess plant to thereby enable a robust wireless communication networkto be used in a process plant or any other environment having HARTcapable devices.

In an embodiment, a process control wireless communication network isdisclosed which comprises a base node, a field node, an environmentalnode and a host. The base node is communicatively coupled to the host.The base, field and environmental nodes each comprising a wirelessconversion unit and a wireless transceiver. The wireless transceivers ofthe base, the field and environmental nodes effect wirelesscommunication among the base, field and environmental nodes. The fieldnode comprises at least one field device providing process controlleddata. The environmental node comprises at least one field deviceproviding data regarding environmental factors that may effect operationof the wireless communication network.

In a refinement, the network also comprises a repeater node comprising awireless conversion unit in a wireless transceiver. The repeater nodeeffects wireless communications amongst the base, field andenvironmental node.

In another refinement, the environmental node comprises a plurality offield devices, each providing data selected from the group consisting oftemperature, barometric pressure, humidity, rainfall and radio frequencyambient noise.

In another refinement, at least some of the field devices are HARTprotocol devices. In another refinement, at least some of the fielddevices are FIELDBUS™ protocol devices.

In another refinement, the network comprises a plurality ofenvironmental nodes strategically placed about a process area forcommunicating environmental data for different locations within theprocess area.

In a refinement, the base, environmental and field nodes form a meshcommunications network, providing multiple communication pathway optionsbetween any two wireless nodes. In another refinement, the base,environmental and field nodes form a point-to-point communicationsnetwork. In yet another refinement, the network comprises a switchdevice to convert the base, environmental and field nodes from a meshcommunications network to a point-to-point communications network andvice versa.

Communication tools are also disclosed to enable an operator to view agraphic of the wireless communication system to easily determine theactual wireless communication paths established within a process plant,to determine the strength of any particular path and to determine orview the ability of signals to propagate through the wirelesscommunication network from a sender to a receiver to thereby enable auser or operator to assess the overall operational capabilities of thewireless communication network.

In a refinement, the communication tools include one or more ofgraphical topology maps illustrating connectivity between nodes, tabularpresentations showing the connectivity matrix and hop counts and actualmaps showing location and connectivity of the hardware devices. Themonitor that illustrates wireless communications between the base, fieldand environmental nodes of the network may be associated with the basenode or the host. In another refinement, the topology screen displayalso illustrates structural features of the process area or environmentin which the base, field and environmental nodes are disposed. Inanother refinement, the host is programmed to provide a tabular screendisplay listing hop counts for communications between the various nodesof the network.

In another refinement, the wireless communication network is configuredto transmit Fieldbus communication signals between different deviceswithin the process plant to thereby enable a robust wirelesscommunication network to be used in a process plant or environmenthaving Fieldbus capable devices in combination with or instead of HARTcapable devices.

In a refinement, a method for controlling a process is disclosed whichcomprises receiving field data from at least one field device,transmitting the field data wirelessly from a field node to a base node,converting the field data to a different protocol, transmitting thefield data of the different protocol to a routing node, determining atthe routing node an object device for receiving the field data of thedifferent protocol, sending the field data of the different protocol tothe object device.

In another refinement, a method for monitoring a wireless processcontrol network is disclosed which comprises receiving environmentaldata from one or more environmental field devices of an environmentalnode, wirelessly transmitting the environmental data to a base node,transmitting the environmental data to a host, interpreting theenvironmental data at the hose, sending a command from the host to thebase node to adjust at least one operating perimeter of the wirelessnetwork based upon the environmental data, transmitting the command fromthe base node to at least one field node comprising at least one fielddevice for executing said command.

Other advantages and features will be come apparent upon reading thefollowing detailed description and independent claims, an upon referenceto the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

For more complete understanding of this disclosure, reference should notbe made to the embodiments illustrated in greater detail in theaccompanying drawings and described below by way of examples. In thedrawings:

FIG. 1 is a combined block and schematic diagram of a conventionalhardwired distributed control system;

FIG. 2 is a combined block and schematic diagram of a wirelesscommunication network within a portion of a process environment designedin accordance with this disclosure;

FIG. 3 is a diagram of a wireless communication network within a processenvironment illustrating both mesh and point-to-point wirelesscommunications;

FIG. 4 is a block diagram of a mesh and point-to-point enabledcommunication device that may be used to switch between mesh andpoint-to-point communications within the communication network of FIG.3.

FIG. 5 is an example of a geometric topology screen display created by awireless network analysis tool illustrating the wireless communicationsbetween different devices within the wireless communication systemdesigned in accordance with this disclosure;

FIG. 6 is an example screen display presented in tabular form andcreated by a wireless network analysis tool illustrating the number ofhops or the hop count between each of the wireless communication deviceswithin a disclosed wireless communication system;

FIG. 7 is an example of a topology screen display created by a disclosedwireless network analysis tool illustrating the wireless communicationswithin a graphic of a plant layout to enable an operator or other userto view the specific communications occurring within the wirelesscommunication network and potential physical obstacles presented by theplant layout;

FIG. 8 is an example screen display created by a disclosed wirelessnetwork analysis tool allowing a user or operator to specify the channelrouting and identification within the wireless communication network;

FIG. 9 is an example screen display created by a wireless networkanalysis tool illustrating graphical displays of information about thewireless communications between different devices within the wirelesscommunication system to enable a user or operator to analyze theoperational capabilities and parameters of the wireless communicationnetwork; and

FIG. 10 is a block diagram of a wireless communication device thatimplements a HART communication protocol wirelessly using a secondcommunication protocol, e.g. the EMBER® protocol.

It should be understood that the drawings are not to scale and that theembodiments are illustrated by graphic symbol, phantom lines,diagrammatic representations and fragmentary views. In certaininstances, details have been omitted which are not necessary for anunderstanding of the disclosed embodiments and methods or which renderother details difficult to perceive. This disclosure is not limited tothe particular embodiments illustrated herein.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 illustrates a typical hardwired distributed process controlsystem 10 which includes one or more process controllers 12 connected toone or more host workstations or computers 14 (which may be any type ofpersonal computer or workstation). The process controllers 12 are alsoconnected to banks of input/output (I/O) devices 20, 22 each of which,in turn, is connected to one or more field devices 25-39. Thecontrollers 12, which may be, by way of example only, DeltaV™controllers sold by Fisher-Rosemount Systems, Inc., are communicativelyconnected to the host computers 14 via, for example, an Ethernetconnection 40 or other communication link. Likewise, the controllers 12are communicatively connected to the field devices 25-39 using anydesired hardware and software associated with, for example, standard4-20 ma devices and/or any smart communication protocol such as theFieldbus or HART protocols. As is generally known, the controllers 12implement or oversee process control routines stored therein orotherwise associated therewith and communicate with the devices 25-39 tocontrol a process in any desired manner.

The field devices 25-39 may be any types of devices, such as sensors,valves, transmitters, positioners, etc. while the I/O cards within thebanks 20 and 22 may be any types of I/O devices conforming to anydesired communication or controller protocol such as HART, Fieldbus,Profibus, etc. In the embodiment illustrated in FIG. 1, the fielddevices 25-27 are standard 4-20 mA devices that communicate over analoglines to the I/O card 22A. The field devices 28-31 are illustrated asHART devices connected to a HART compatible I/O device 20A. Similarly,the field devices 32-39 are smart devices, such as Fieldbus fielddevices, that communicate over a digital bus 42 or 44 to the I/O cards20B or 22B using, for example, Fieldbus protocol communications. Ofcourse, the field devices 25-39 and the banks of I/O cards 20 and 22could conform to any other desired standard(s) or protocols besides the4-20 mA, HART or Fieldbus protocols, including any standards orprotocols developed in the future.

Each of the controllers 12 is configured to implement a control strategyusing what are commonly referred to as function blocks, wherein eachfunction block is a part (e.g., a subroutine) of an overall controlroutine and operates in conjunction with other function blocks (viacommunications called links) to implement process control loops withinthe process control system 10. Function blocks typically perform one ofan input function, such as that associated with a transmitter, a sensoror other process parameter measurement device, a control function, suchas that associated with a control routine that performs PID, fuzzylogic, etc. control, or an output function that controls the operationof some device, such as a valve, to perform some physical functionwithin the process control system 10. Of course hybrid and other typesof function blocks exist. Groups of these function blocks are calledmodules. Function blocks and modules may be stored in and executed bythe controller 12, which is typically the case when these functionblocks are used for, or are associated with standard 4-20 mA devices andsome types of smart field devices, or may be stored in and implementedby the field devices themselves, which may be the case with Fieldbusdevices. While the control system 10 illustrated in FIG. 1 is describedas using function block control strategy, the control strategy couldalso be implemented or designed using other conventions, such as ladderlogic, sequential flow charts, etc. and using any desired proprietary ornon-proprietary programming language.

As evident from the discussion of FIG. 1, the communications between thehost workstations 14 and the controllers 12 and between the controllers12 and the field devices 25-39 are implemented with hardwiredcommunication connections, including one or more of HART, Fieldbus and4-20 mA hardwired communication connections. However, as noted above, itis desirable to replace or augment the hardwired communicationconnections within the process environment of FIG. 1 with wirelesscommunications in an manner that is reliable, that is easy to set up andconfigure, that provides an operator or other user with the ability toanalyze or view the functioning capabilities of the wireless network,etc.

FIG. 2 illustrates a wireless communication network 60 that may be usedto provide communications between the different devices illustrated inFIG. 1 and, in particular, between the controllers 12 (or the associatedI/O devices 22) of FIG. 1 and the field devices 25-39, between thecontrollers 12 and the host workstations 14 or between the hostworkstations 14 and the field devices 25-39 of FIG. 1. However, it willbe understood that the wireless communication network 60 of FIG. 2 couldbe used to provide communications between any other types or sets ofdevices within a process plant or a process environment.

The communication network 60 of FIG. 2 is illustrated as includingvarious communication nodes including one or more base nodes 62, one ormore repeater nodes 64, one or more environment nodes 66 (illustrated inFIG. 2 as nodes 66 a and 66 b) and one or more field nodes 68(illustrated in FIG. 2 as nodes 68 a, 68 b and 68 c). Generallyspeaking, the nodes of the wireless communication network 60 operate asa mesh type communication network, wherein each node receives acommunication, determines if the communication is ultimately destinedfor that node and, if not, repeats or passes the communication along toany other nodes within communication range. As is known, any node in amesh network may communicate with any other node in range to forwardcommunications within the network, and a particular communication signalmay go through multiple nodes before arriving at the desireddestination.

As illustrated in FIG. 2, the base node 62 includes or iscommunicatively coupled to a work station or a host computer 70 whichmay be for example any of the hosts or workstations 14 of FIG. 1. Whilethe base node 62 is illustrated as being linked to the workstation 70via a hardwired Ethernet connection 72, any other communication link maybe used instead. As will be described in more detail later, the basenode 62 includes a wireless conversion or communication unit 74 and awireless transceiver 76 to effect wireless communications over thenetwork 60. In particular, the wireless conversion unit 74 takes signalsfrom the workstation or host 70 and encodes these signals into awireless communication signal which is then sent over the network 60 viathe transmitter portion of the transceiver 76. Conversely, the wirelessconversion unit 74 decodes signals received via the receiver portion ofthe transceiver 76 to determine if that signal is destined for the basenode 62 a and, if so, further decodes the signal to strip off thewireless encoding to produce the original signal generated by the senderat a different node 64, 66 or 68 within the network 60.

As will be understood, in a similar manner, each of the othercommunication nodes including the repeater nodes 64, the environmentalnodes 66 and the field nodes 68 includes a communication unit 74 and awireless transceiver 76 for encoding, sending and decoding signals sentvia the wireless mesh network 60. While the different types of nodes 64,66, 68 within the communication network 60 differ in some importantways, each of these nodes generally operates to receive wirelesssignals, decode the signal enough to determine if the signal is destinedfor that node (or a device connected to that node outside of thewireless communication network 60), and repeat or retransmit the signalif the signal is not destined for that node and has not previously beentransmitted by that node. In this manner, signals are sent from anoriginating node to all the nodes within wireless communication range,each of the nodes in range which are not the destination node thenretransmits the signal to all of the other nodes within range of thatnode, and the process continues until the signal has propagated to allof the nodes within range of at least one other node.

However, the repeater node 64 operates to simply repeat signals withinthe communication network 60 to thereby relay a signal from one nodethrough the repeater node 64 to a second node 62, 66 or 68. Basically,the function of the repeater node 64 is to act as a link between twodifferent nodes to assure that a signal is able to propagate between thetwo different nodes when these nodes are not or may not be within directwireless communication range of one another. Because the repeater node64 is not generally tied to other devices at the node, the repeater node64 only needs to decode a received signal enough to determine if thesignal is a signal that has been previously repeated by the repeaternode (that is, a signal that was sent by the repeater node at a previoustime and which is simply being received back at the repeater nodebecause of the repeating function of a different node in thecommunication network 60). If the repeater node has not received aparticular signal before, the repeater node 64 simply operates to repeatthis signal by retransmitting that signal via the transceiver 74 of therepeater node 64.

On the other hand, each of the field nodes 68 is generally coupled toone or more devices within the process plant environment and, generallyspeaking, is coupled to one or more field devices, illustrated as fielddevices 80-85 in FIG. 2. The field devices 80-85 may be any type offield devices including, for example, four-wire devices, two-wiredevice, HART devices, Fieldbus devices, 4-20 mA devices, smart ornon-smart devices, etc. For the sake of illustration, the field devices80-85 of FIG. 2 are illustrated as HART field devices, conforming to theHART communication protocol. Of course, the devices 80-85 may be anytype of device, such as a sensor/transmitter device, a valve, a switch,etc. Additionally, the devices 80-85 may be other than traditional fielddevices such as controllers, I/O devices, work stations, or any othertypes of devices.

In any event, the field node 68 a, 68 b, 68 c includes signal linesattached to their respective field devices 80-85 to receivecommunications from and to send communications to the field devices80-85. Of course, these signal lines may be connected directly to thedevices 80-85, in this example, a HART device, or to the standard HARTcommunication lines already attached to the field devices 80-85. Ifdesired, the field devices 80-85 may be connected to other devices, suchas I/O devices 20A or 22A of FIG. 1, or to any other desired devices viahardwired communication lines in addition to being connected to thefield nodes 68 a, 68 b, 68 c. Additionally, as illustrated in FIG. 2,any particular field node 68 a, 68 b, 68 c may be connected to aplurality of field devices (as illustrated with respect to the fieldnode 68 c, which is connected to four different field devices 82-85) andeach field node 68 a, 68 b, 68 c operates to relay signals to and fromthe field devices 80-85 to which it is connected.

In order to assist in the management in the operation of thecommunication network 60, the environmental nodes 66 are used. In thiscase, the environmental nodes 66 a and 66 b includes or iscommunicatively connected to devices or sensors 90-92 that measureenvironmental parameters, such as the humidity, temperature, barometricpressure, rainfall, or any other environmental parameters which mayeffect the wireless communications occurring within the communicationnetwork 60. As discussed in more detail below, this information may beuseful in analyzing and predicting problems within the communicationnetwork, as many disruptions in wireless communications are at leastpartially attributable to environmental conditions. If desired, theenvironmental sensors 90-92 may be any kind of sensor and may include,for example, HART sensors/transmitters, 4-20 mA sensors or on boardsensors of any design or configuration. Of course, each environmentalnode 66 a, 66 b may include one or more environmental sensors 90-92 anddifferent environmental nodes may include the same or different types orkinds of environmental sensors if so desired. Likewise, if desired, oneor more of the nodes 66 a, 66 b may include an electromagnetic ambientnoise measurement device 93 to measure the ambient electromagnetic noiselevel, especially at the wavelengths used by the communication network60 to transmit signals. Of course, if a spectrum other an RF spectrum isused by the communication network 60, a different type of noisemeasurement device may be included in one or more of the environmentalnodes 66. Still further, while the environmental nodes 66 of FIG. 2 aredescribed as including environmental measurement devices or sensors90-93, any of the other nodes 68 could include those measurement devicesso that an analysis tool may be able to determine the environmentalconditions at each node when analyzing the operation of thecommunication network 60.

Using the communication system 60 of FIG. 2, an application running onthe workstation 70 can send packets of data to and receive packets ofwireless data from the wireless base card 74 residing in a standardcontroller 75 at the base node 62. This controller 75 may be, forexample, a DeltaV controller and the communications may be the same aswith a standard I/O card via the Ethernet connection to the DeltaVcontroller. The I/O card in this case includes a wireless base card 74,though as far as the controller and PC Application goes, it appears as astandard HART I/O card.

In this case, the wireless card 74 at the base node 62 encodes the datapacket for wireless transmission and the transceiver 76 as the base node62 transmits the signal. FIG. 2 illustrates that the transmitted signalmay go directly to some of the field nodes such as nodes 68 a and 68 b,but may also propagate to other field nodes, such as nodes 68 c, via therepeater node 64. In the same manner, signals created at and propagatedby the field nodes 68 may go directly to the base node 60 and otherfield nodes 66 or may be transmitted through other nodes such as therepeater node 64 or another field node before being transmitted to thebase node 62. Thus, the communication path over the wireless network 60may or may not go through a repeater node 64 and, in any particularcase, may go through numerous nodes before arriving at the destinationnode. If a sending node is in direct communication reach of the baseunit 62, then it will exchange data directly. Whether or not the packetspass through a repeater node 64 is completely transparent to the enduser, or even to the card firmware.

It will be noted that FIG. 2 is a schematic diagram and the placement ofthe environmental nodes 66 a, 66 b relative to the field nodes 68 a-68 care not intended to be relative to their actual placement in an actualprocess control area. Rather, the environmental nodes 66 a, 66 b (andother environmental nodes not pictured or a single environmental node)are intended to be placed about the process control area in a logicaland strategic manner as shown in FIG. 7. In other words, environmentalnodes 66 should be placed at spaced apart location, such as at opposingends of large obstacles or pieces of equipment or near roadways whereinterference from moving vehicles may be present. Also, environmentalnodes should be placed both indoors and outdoors if applicable. Thenetwork of environmental nodes 66 is intended to be used by the basenodes 62 and host 70 as a means for monitoring the operation of thewireless network 60 and modifying the operation of the network 60 byincreasing or decreasing signal strength, gain, frequency etc.

It will be noted that the field nodes 68 are placed at or near variousprocess stations. The node 68 may be important safety devices or maybeused to monitor and/or control various processes. Further, more than onerepeater node 64 may be used and, in fact, FIG. 2 is but one example asit may be determined that it only single environmental node 66 isnecessary, that more than one or no repeater nodes 64 are needed andthat fewer than three or more than three field nodes 68 are necessary.

Turning to FIGS. 3 and 4, it is anticipated that the wireless network 60of FIG. 2 may need to be switched back and forth between mesh andpoint-to-point communication modes. FIG. 3 illustrates a network 100with a base node 101 in communication with repeater nodes 102 a, 102 b,102 c. The repeater nodes 102 a-102 c are, in turn, in communicationwith a plurality or a cluster of either environmental nodes, field nodesor combination of the two as shown generally at 104. A point-to-pointwireless communication system for FIG. 3 is shown in solid line while analternative mesh configuration is shown in solid line.

Turning to FIG. 4, a switch device 105 is shown schematically which maybe disposed in the base mode 101 in addition to the wireless andtransceiver (not shown). The switch 105 is intended to convert thenetwork 100 from a mesh wireless network as shown by the phantom linesin FIG. 3 to a point-to-point wireless network as shown by way ofexample in the solid line of FIG. 3. Of course, the point-to-pointcommunications can be configured in any manner and the solid lines shownin FIG. 3 are but one example. The switch device 105 as shown in FIG. 4can include an electronic switch element 106 that shifts the device 105between a mesh wireless transceiver 76 a and a point-to-point wirelesstransceiver 76 b.

As noted above, the disclosed network 60 includes a base node 62 andhost 70 that may be programmed to provide a variety of graphicallyinterfaces that will be useful to the operator. Examples of suchgraphical interfaces are shown in FIGS. 5-9. Turning to FIG. 5, ageometric topology screen display 110 is disclosed which illustrates awireless network between a base node BA and a plurality of other nodeswhich may be one or more repeater nodes, field nodes and environmentalnodes numbered in FIG. 5 as 03, 04, 05, 06, 07, 08, 09, 10 (0A), and 11(0B). The topology display 110 of FIG. 5 illustrates a successfulcommunication between two nodes with a solid, dark line, one example ofwhich is the communication between the base node BA and the node 7. Asuccessful communication in one direction only is illustrated by alighter line with cross hatches, one example of which is the linebetween the nodes 03 and 10 (0A). An unsuccessful communication isindicated by a dashed or phantom line, one example of which is the lackof communication illustrated by the dashed line between nodes 05 and 11(0B). FIG. 5 also illustrates the “hop count” between nodes. Forexample, looking at nodes 04 and 07, the dashed or phantom line betweennodes 04 and 07 of FIG. 5 make it clear that there is no direct wirelesscommunication between nodes 04 and 07 while there is communicationbetween nodes 04 and 05 and one-way communication between nodes 05 and07. Thus, for one-way communication between nodes 04 and 07, there is ahop count of 2 (node 04 to node 05 and node 05 to node 07).Alternatively, for two-way communication between nodes 04 and 07, thereis also a hop count of 2 (node 07 to node 03 and node 03 to node 04).Obviously, the lower the hop count the better and the more reliable thecommunication.

The hop counts for the network shown in FIG. 5 are shown in tabular formin FIG. 6. The nodes labeled 10 and 11 in FIG. 5 are also indicated as0A and 0B in FIG. 6. The base node BA communicates directly with nodes03 through 0B and therefore the hop count between the base node BA andany one of 03 through 0B is one is indicated in the top row of the tableshown in FIG. 6. Turning to the second row of the table of FIG. 6, itwill be noted that the hop count between node 03 and any of the othernodes is also 1 as node 3 of FIG. 5 includes no dashed lines emanatingfrom it. However, turning to the third row of the table of FIG. 6 andreferring to FIG. 5, it will be noted that node 04 includes a dashedline extended between node 04 and node 07 and therefore directcommunication between node 04 and node 07 is not possible. Thus, toconnect from node 04 to node 07, the communication precedes through node05 for a hop count of 2. Still further, because there is a light coloredcross-hatched line between node 04 and node 09 in FIG. 5, direct two-waycommunication between node 04 and 09 is not possible. Accordingly, fortwo-way communication between nodes 04 and 09, the communication mustpass through node 08 as indicated in the table of FIG. 6. All of theentries that are circled in FIG. 6 indicate a hop count of 2.

Turning to FIG. 7, a topology map similar to that shown in FIG. 5 isillustrated as an overlay of a map for an actual process environment.Specifically, each point is the location of 1 of the 9 nodes show inFIG. 5 and listed in the table of FIG. 6. FIG. 7 provides the operatorwith an opportunity to view the wireless connectivities within thecontext of the actual operating environment. Global positioning systemreference points are indicated at 111, 112 so actual distances betweenthe nodes can be determined.

Turning to FIG. 8, the field devices 80-85 and 90-93 may appear to thebase node 62 or host 70 as a standard HART device. This enables standardapplications such as AMS software to run seamlessly on top of thewireless network 60. To utilize the AMS software, the wireless fieldnodes 66 and 68 need to know how to route messages. This is accomplishedby utilizing a routing map 120 as illustrated in FIG. 8. This map 120 isstored in the nonvolatile memory of the base unit 62, but also could bestored in the memory of the host 70. The actual routing takes advantageof incorporating a base card that is identical to an 8 channel HARTcard. The routing tool then maps 8 virtual HART channels to remote fieldnodes and their channels. FIG. 8 illustrates a mapping configuration for8 different devices. Each Field type wireless node may include 4different HART channels, though the field device will have one uniqueID. The actual target channel is embedded in the wireless packet. EachID for each wireless unit is based on 2 bytes. The first byte is thenetwork number and correlates to an actual radio channel in the wirelessinterface. The number of the first byte can range from 1 to 12. Thesecond byte is the identification of the node in the network and canrange from 1 to 15. When a node is initialized for a first time, itsdefault address is 010F, which mean network 1, address 15. The exceptionto this address scheme is the base unit which always has BA as its firstbyte, the second byte representing which network the device is in.

Turning to FIG. 9, another graphical presentation 130 for display at thehost 70 (FIG. 1) is shown. 4 graphs are shown, one on top of each otherwith time being plotted on the x-axes. The top graph 131 plots a totalhop count for the entire system which, as shown, averages about 72 orslightly less. An increase in the hop count would provide a warning tothe operator. The other graphs in FIG. 9 provide environmentalinformation from the environmental node 66 shown in FIG. 2. The graph132 provides a reading of barometric pressure; the graph 133 provides areading of humidity; and the graph 134 provides a reading of the generalRF background noise within the operating frequency band. Otherenvironmental indications not presented in FIG. 9 could be temperatureand rainfall.

Turning to FIG. 10, it will be noted that many of the devices 80-85shown in FIG. 2 would be HART field devices, and therefore the fieldnode 68 will be sending a HART signal to either a repeater node 64 ordirectly to a conversion node 140 which, in the embodiment shown in FIG.10, may be a separate element or may comprise part of the base node 62.A HART signal may also be sent from an environmental node 66 as shown.The conversion node 140 includes software to convert the HART signal toa different protocol, e.g., the EMBER protocol used with low-powerwireless networking software and radio technology. Seehttp://www.ember.com/. Of course, other protocols are available and willbe apparent to those skilled in the art. The conversion node 140converts the HART signal to an EMBER data packet at 141. The data packetincludes an origin indication 142 and a destination indication 143 whichis determined by software either in the base node 62 or in theconversion node 140. The HART message 143 is sandwiched between theorigin data 142 and destination data 143. The signal is then sent to arouting node 145 which determines, from the destination information 143,which object device 146 to send the data to. The routing node 145 thentransmits the data through one or more repeaters 64 and/or field nodes68 to the object device 146. One type of software that could be used toconvert the field device signal from one protocol (HART) to anotherprotocol is the GTS software sold by Acugen(http://www.acugen.com/jts.htm).

Although the present invention has been described with reference topreferred embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention.

1. A method for controlling a process using a wireless communicationsnetwork, the method comprising: receiving field data from at least onefield device; transmitting the field data wirelessly from a field nodeto a base node; converting the field data to a different protocol;transmitting the field data of the different protocol to a routing node;determining at the routing node an object device for receiving the fielddata of the different protocol; and sending the field data of thedifferent protocol to the object device.
 2. The method of claim 1,wherein the at least one field device transmits the field data using theHART communication protocol and the field data is converted from theHART communication protocol to the different protocol by the base node.3. The method of claim 1, wherein the field node, the base node and therouting node form a mesh wireless communications network.
 4. The methodof claim 1, wherein the field node, the base node and the routing nodeform a point-to-point wireless communications network.
 5. The method ofclaim 1, wherein each field device of the field node is a HART protocoldevice.
 6. The method of claim 1, wherein each field device of the fieldnode is a Fieldbus protocol device.
 7. The method of claim 1, whereinthe field data is converted from the HART communication protocol to thedifferent protocol by a conversion node.
 8. The method of claim 7,wherein the field data is a HART signal.
 9. The method of claim 7,wherein the conversion node converts the HART signal to an EMBER datapacket.
 10. The method of claim 1, wherein the routing node sends thefield data through one or more repeaters and the field node.